Population genetics ofGaultheria shallonin British Columbia and the implications for management using biocontrol

Abstract

Gaultheria shallon Pursh. (salal), an ericaceous shrub native to the Pacific Northwest, often out-competes regenerating conifer species in managed forests. A naturally occurring fungus, Valdensinia heterodoxa Peyronel, is being considered as a potential biocontrol agent for salal. Knowledge of the genetic diversity and population structure of salal will help assess the effectiveness and the potential risks of using a biocontrol agent in natural populations. Salal samples were collected from five populations, four on Vancouver Island and one on coastal mainland British Columbia. DNA fingerprints were obtained based on 230 amplified fragment length polymorphisms (AFLPs), of which 99.1% were variable. While salal has been reported to be a polyploid, it is likely that over time it is moving toward a diploid state. Based on a comparison of allele frequencies with known diploids, the AFLP loci used in this study appear to follow a diploid pattern; however, the levels of variation reported in this study may be an underestimation depending on the ploidy of salal. An intensively sampled population on Vancouver Island (Shawnigan Lake) showed isolation by distance and low kinship correlations, indicative of more sexual reproduction than expected for a predominantly clonal population. Our findings suggest that salal may be clonal at a very local scale (less than 5 m), and that with high levels of diversity within populations and little differentiation among populations, developing an effective biocontrol for salal may be challenging.Key words: population structure, genetic diversity, AFLP, biocontrol, Gaultheria shallon.